Tunable excited states in moiré superlattices
Max Planck Quantum Matter Seminar
- Date: Mar 3, 2022
- Time: 03:00 PM - 04:00 PM (Local Time Germany)
- Speaker: Xiaoqin Elaine Li
- University of Texas at Austin
- Location: online via Zoom
- Host: Gregor Jotzu

In van der Waals bilayers, the strict requirement of lattice matching at
the interface is lifted. The periodic changes in atomic alignment lead
to the formation of an in-plane superlattice, known as the moiré
superlattice. The twist angle acts as a unique knob to control the
material properties. Instead of focusing on the correlated ground states
often discussed in the literature, I will discuss how excited states
and collective excitations are modified. The lifetimes of bound
electron-hole pairs (i.e. excitons) can be varied by one order of
magnitude when the twist angle of a MoSe2/WSe2 bilayer is varied from 1°
to 3.5°. The phonon spectra evolution in MoS2 bilayers reflects lattice
reconstruction over a surprisingly large range of twist angles from
zero to 6°. If time permits, I will share some new results on
topological magnons that exhibit long lifetimes near the Brillouin zone
boundary.